Camera Parts: Rewind Release

A rewind release button is one of the camera parts found on both manual and automatic film camera. However, it's exact function differs slightly between the two.

Rewind Release on a Manual Camera

When film is loaded in a camera, winding sprockets pull the film from
the cassette onto the take-up spool. The gearing in these prevents the
film from going the opposite direction. However, once the roll is
complete, the gears must be release so the film can be rewound. A rewind
release button disengages the gears on the take-up spool and the
winding sprockets. Once depressed, the film can be rewound into the
cassette using the film rewind knob.

A second purpose for the rewind release button is if a photographer
wishes to rewind their film before completing the roll. Like before,
this process requires pressing the rewind release button while rewinding
with the film rewind knob.

Rewind Release on an Automatic Camera

On automatic cameras, this is usually referred to as a midroll rewind
button. It's purpose is the second purpose listed above: rewinding a
roll before it is complete. Usually, the button needs to be depressed
for some time before rewinding begins. This is to prevent accidental
touches.

Automatic camera will rewind a finished roll automatically, so no button press is needed for normal operation.